Although the industry has made significant improvements in the field of fuel metering, various levels of government have, nevertheless, unilaterally established strict limits on vehicular engine exhaust emissions such as, for example, oxides of nitrogen, unburned hydrocarbons and carbon monoxide. There are, obviously, many influencing factors collectively determining the degree of such exhaust emissions from any particular vehicle and engine. For example, engine spark timing, mode of engine operation (whether hot or cold and whether accelerating or decelerating), fuel metering head in the fuel bowl, degree of pressure drop across air intake filter, and the general condition of the engine intake and exhaust valves are just some of the variables which will determine the degree of exhaust emission. The prior art has suggested various means, methods and apparatus for reducing exhaust emissions due to the aforementioned factors. However, even with the adoption of such proposals by the prior art, it has been found that problems still existed with regard to meeting such governmentally imposed limits of exhaust emissions.
It has now been discovered that there is another factor which can lead to increased exhaust emission regardless of how precisely or carefully the engine components are manufactured and regardless of how carefully and precisely the carburetor or other fuel metering device, to be used with such an engine, are manufactured and calibrated.
Such an additional factor is the unauthorized tampering with certain of the metering restrictions (which were precisely determined during manufacture) by individuals, after the carburetor or other fuel metering device has been sold and placed into actual use. Such individuals were found to often "adjust" the carburetor or other fuel metering device in order to obtain what they considered "better" engine performance.
This usually meant that such individuals tried to obtain a richer (more) fuel flow to the engine than that as established by the engine and/or carburetor and/or fuel control manufacturer. The system within, for example, the carburetor which could be most easily manipulated by such individuals is the idle fuel system since it possessed an adjustable needle valve generally in the idle fuel discharge port.
The elimination of such adjustable needle valves would, in turn, create serious difficulties in attempting to properly calibrate the carburetor during its manufacture and, attendantly, greatly increase the cost thereof.
Accordingly, the invention as herein disclosed and claimed is primarily directed to the solution of the problems arising relative to and out of such adjustable needle-type valves as well as other related and attendant problems. However, it should be made clear that even though the problem of unauthorized tampering type of adjustments of needle-type valves gave rise to the invention, neither the invention nor the practice thereof is limited to needle-type valve structures nor to any type of fuel metering or supply apparatus.